1. Field of the Invention
This invention relates to a process for converting an alkane to carboxylic acids by subjecting said alkane to the action of molecular oxygen in the presence of acetic acid but in the absence of a heavy metal oxidation catalyst.
2. Description of the Prior Art
The oxidation of an alkane with molecular oxygen to obtain carboxylic acids selectively has been difficult. Luther et al in U.S. Pat. No. 1,864,079 have oxidized an alkane in the presence of from two to 20 percent of a lower acid, such as formic acid, acetic acid or propionic acid, or mixtures thereof, preferably in the presence of an oxidation catalyst, to obtain a product predominating in alcohols, which, in turn, react with said lower acid to form the corresponding esters thereof. Fanning, in Canadian Pat. No. 773,592, states that such oxidation is difficult, that the same cannot be carried out in the presence of acetic acid, even when a heavy metal catalyst is employed, and that these difficulties can be avoided when the alkane is oxidized in a system containing a combination of acetic and propionic acids, because this mixture serves to maintain a single-phase system. In U.S. Pat. No. 3,196,182 Cox is interested in oxidizing a lower hydrocarbon, such as butane, in a manner so as to obtain higher ratios of methyl ethyl ketone to acetic acid by contacting the hydrocarbon with an oxygen-containing gas in the presence of a liquid recycle medium and/or a normally liquid organic vehicle, which serves to maintain the hydrocarbon in essentially liquid phase, in an elongated reaction zone while eliminating backmixing, thus establishing a flow pattern that he characterizes as "plug flow".